Corrosion prevention method



Patented Jan. 22, 1952 CORROSION PREVENTION METHOD Aaron ,Wachter, Oakland, Galifl, and Wilfrid W. Newschwander, Ellensburg, Wash assignors to Shell Development Company, Emeryville, Calif., a corporation of Delaware No Drawing. Application March 5, 1951, Serial No. 214,032

11. Claims. (01. 2528.55)

This invention relates to a method of corrosioninhibition of a ferruginous material, e. g., steel, while in contact with an agitated fluid system of liquid or liquefied phases and an atmosphere of aqueous carbonic acid and/or carbon dioxide. More particularly, the invention applies to corrosion-prevention otmetal equipment normally used in operating gas-condensate light gasoline wells, whereby such corrosion-prevention is effected during the conventional operation of these wells.

In recent years, the problem of preventing corrosion of ferruginous materials, e. g., steel, in the above-described systems as indicated above has -been technically noted as very serious. No satisfactory method is known for preventing corrosion of tubing in operating wells under corrosive conditions indicated above.

It is an object of the present invention to provide an inexpensive and industrially feasible method of corrosion-inhibition of ferruginous metals in a system in which an agitated flowing mixture of non-oxidizinggases, a liquefied hydrocarbon phase and an aqueousjcarbonic acid phase come in contact with such ferruginous metal. It is another object to overcome the disadvantages of prior art practices peculiar to corrosioninhibition applied in operation of gas-condensate wells. A further object is to provide an inexpensive and industrially feasible corrosioninhibition treatment of iron-containing metals, e. g., steel, contacting the above-specified system as it occurs in the case of an operating gascondensate well.

It has now been discovered that corrosion which is caused by contact of ferruginous metal with a system of nonroxidizing gases and an agitated flowing mixture of a liquefied hydro carbon. phase and an aqueous carbonic acid phase, can be inhibited by introducing (continue ously or intermittently) into this system a minor but corro sion-inhibiting amount of a high mol cu ar weight oi -so uble or anic vsu fo salt.

Described more specifically, it has been found that corrosion of iron-containing. metal tubin and we'll-head fittingsv :in a flowing gas-condensate well containing water and carbon dioxide is inhibited substantially-by mixing with the fluid mixture in :the well a salt of a high molecular weight. oil-soluble sulfonic acid, and particularly in the case of those operating gas condensate wells-wherein there is a liquefied hydrocarbon phase-aswell as a liquid waterphase.

The liquefied hydrocarbon phase in gas-condensate wells normally comprises mixtures of liquid methane, ethane, propane, butane and heavier hydrocarbon condensates up to and including light gasolines having up to about eight carbon atoms. Normally gaseous hydrocarbons are partly liquefied in the well because of the pressures ordinarily existing therein. A typical gas-cpndensate well produces between twenty and thirty barrels of a liquefied hydrocarbon phase per million cubic feet of gas (MMQF), at a typical well-head temperature and pressure. The temperatures at the bottom of the well usual apes i o a eut 8 oa out 2 average temperatures at the well-head being usually in the range from about 515 C. to about C. Pressures a condensate well usually range tron; about 1,000 to about 7,000 pounds per square inch absolute. A typical well may have a bottom-hole pressure of about 2,700 p. s. i. a. an d ar fiowing tubing pressure of about. 2,000 p. s. i. a. The pressure increases the ratio of gaseous carbon dioxide (present in condensate ells. w ic i sol e n th eq eu Phas al o p e nt there ne l-hea co d mis he e is usually a ran e ro a o ve to about twenty a lon r hi of id Wate per MMCF of. gas produced. his q i Wat phase dissolves carbon dioxide thus providing the aqueous carbonic acid phase. The latter nsually has a pH value ranging from about 3.3 to about a pH of 5.5 This aqueous phase may also .contain sodium chloride and other electrolytes, the usual amounts of which are well lcnown to the art. Aqueous carbonic acid phase mixed with agitated liquefied hydrocarbon phase and gases is usually distributed throughout the flowing systemof the Well.

The sulfonate salts to be employed in the practice of this invention should have a molecular weight-of at least 400 and should not exceed about 1500; preferably the molecular weight range should :be from about 400 toabout 880. In order to ensureoil-solubility, the sulionate salt should have an oleophilic residue or radical attached to the .sulfonate nucleus, preferably comprising at least one hydrocarbon radical having about 16 or more carbon atoms. The oleophilic radical or residue preferably comprises monoor poly: aromatic and/or naphthenic ring radicals which are alkylated; however, it may be a saturated, or olefinic aliphatic hydrocarbon radical. Any one hydrocarbon radical in the sulfonate salt should not contain a hydrocarbon radicalwhich is longer than an approximately thirty-carbon straight-chain radical, and the total carbon con- 3 tent of the sulfonate salts employed should not be more than approximately ninety carbon atoms.

Although any salt (metallic or non-metallic) of an oil-soluble sulfonate as described above may be used, it has been found that the above-specified corrosion-inhibition of steel is particularly achieved by introducing into the system an oil-soluble organic sulfonate salt of a base selected from the inorganic group of basic cations made up of sodium, potassium, lithium, calcium, strontium, barium and ammonium ions, and from the organic group of basic cations made up of organo-nitrogen base ions such as those of the amines, quaternary ammonium ions and the heterocyclic nitrogeneous basic ions. Of these basic cations used to form the sulfonate salt, the strong base metal cations of the type of alkali and alkaline earth metal cations are preferred; however, in many cases, the salts of organo-nitrogen bases and the appropriate sulfonic acids have been found to be eminently useful.

The oil-soluble sulfonates of this invention may contain two and even three sulfonate salt groups so long as they are substantially concentrated toward one end or in one anterior portion of the agent molecule and sufiicient oil-solubility of the molecule as a Whole is present. Preferably, the number of sulfonate groups per molecule is limited to no more than two.

Particularly significant corrosion-prevention in practice of the invention has been obtained with oil-soluble monoand di-sulfonate salts at concentrations below 0.1 Wt. as low as OLOOl wt. and even lower, based on the liquefied hydrocarbon phase. Amounts up to and even more than 1% may be used with benefit if the economics permit it.

By an oil-soluble organic residue in the present agents is meant any oil-solubilizing and substantially water-insolubilizing organic radical containing, or consisting of at least sixteen carbon atoms; preferably it is composed of alkylated aryl or alicyclic rings or heterocyclic rings; it may be less desirably an alkyl group. As an aryl containing oil-solubilizing radical there may be used a benzene or naphthalene ring attached to one or more alkyl groups, wherein one of the latter may serve as an alkylene group, attaching the residue to the sulfonate salt group. The term aliphatic side-chain as used herein means a side-chain which is an alkyl, cycloalkyl or mixed alkyl-cycloalkyl radical and which may contain unsaturated linkages.

Hetero-atoms such as oxygen, sulfur, or nitrogen may be present in, or provide interconnecting links in the organic residue connected to the one or more sulfonate salt groups so long as the oil-solubility of the molecule as a whole is retained and the direction of polarity afiorded by the sulfonate group is retained.

An oil-soluble sulfonate salt for the present invention may be prepared by neutralization of an oil-soluble sulfonic acid. The oil-soluble sulfonic acids are hydrocarbon sulfonic acids (which may contain heterogroups) having a solubility in a lubricating mineral oil of SAE. 30 grade of at least approximately 0.1 wt. at 25 C. Particularly efiective for the purpose of the invention are those sulfonates which have an oilsolubility of about 1 wt. up to about5 wt. and even higher. The solubility may be as high as 50 wt. or higher in alubricating oil or in a diesel oil. Some of these oil-soluble sulfonic acids may also be partially soluble in water: howcarbon atoms.

ever, the present sulfonic acids or their salts do not include those salts which are miscible with water in all proportions. Solubility of many of the present agents in both oils and water results from their having intra-molecularly both a strong water-solubilizing' radical and a strong oil-solubilizing radical (or radicals).

The so-called mahogany acids (oil-soluble petroleum sulfonic acids) yield salts useful as the agents in this invention. The mahogany acids include particularly the oil-soluble aromatic sulfonic acids from petroleum. Many of the aromaticsulfonic acids from petroleum have cycloalkyl (i. e., naphthenic) groups in the sidechain(s) attached to the benzene ring. The mahogany acids also include non-aromatic sulfonic acids produced in conventional sulfuric acid refining of lubricating oil distillates and from the industrial use of fuming sulfuric acid in the manufacture of petrolatum. The industrial production of oil-soluble mahogany sulfonates from petroleum is well understood in the art and described in the literature.

Non-aromatic long-chain paraflinic sulfonates which are eiTective agents in the practice of this invention, may also be prepared by other well known methods, such as may be represented by the equation:

where R is a long-chain hydrocarbon residue. The thus produced alkyl-sulfonyl chlorides upon saponification give desired metal sulfonate salts. Suitable long-chain sulfonates may also be produced by Well-known Strecker reactions in which sodium, potassium or ammonium sulfite are reacted With a long-chain organic chloride. Some suitable sulfonates produced by this method are:

OaoHelS OaNa A preferred class of sulfonatesalts for the present invention are those derived from monosulfonic aromatic acids having alkyl and/or cycloalkyl radicals attached to the aromatic 7 ring, and a molecular weight of at least approximately 400. Of particular utility are such sulfonate salts having a molecular weight of about 450 to about 650, so long as the aromatic-sulfonate nucleus therein has a hydrocarbon chain attached thereto having not more than about 30 carbon atoms; preferably, the sulfonate molecule contains a total of not more than about 65 Of these petroleum-derived sulfonates, the substantially water-insoluble calcium salts thereof are particularly valuable for the purpose of this invention. Those sulfonates which contain on the average at least one aromatic nucleus and at least one naphthenic group per molecule, as obtained from a naphthenlcaromatic oil are especially effective.

Particularly: preferred examples. of sulfonate salts as. agents in the present invention are:

octadecylbenzene sulfonate, octadecyltetralinsulfonate, disodium octadecyltetralindisulfonate, etc. The. disodium octadecyltetralindisulfonate exhibits prevention of steel corrosion when tested even at as low a concentration as 0.03 to 0.01 wt.'% (based on. the.- liquefied hydrocarbon) in a. carbonic; acid. phase-light gasoline phase agitated system.

the case of the amine or quaternary ammonium. base sulfonates, the amine or quaternary ammonium residue may be short, or it may have a long organic residue which may be the same or substantially similar to the organic residue attached; to the sulfur in the sulfonate portion of the salts The presence of an oil-solubilizing organic group, particularly of a hydrocarbon radicahof 16.0r more carbon atomsin the nitrogen base residue, surprisingly enough does not.

substantially detract from the present corrosioninhibiting efiect of the sulfonate salts even though the ratioof the sulfonate nucleus to total molecular; weight is greatly decreased. In gene ial; the;- same oil-soluble sulfonic acids as used in; the; sulionates described; above may; be coupled with organic N-containing bases to form the corresponding N-base sulfonates. amines; for forming thesalts are the primary, secondaryand; tertiary amines. Among these, dlmethylamine, diisopropyl amine, ethyl amine, trimethyl amine, cyclohexylamine and similar amines are preferred. Illustrative long-chain amines are: lauryl amine, stearyl amine, etc. Illustrative examples of suitablev heterocyclic nitrogeneousbases are: pyridines, oxazoles, oxazolines, oxazinesdiazoles, pyrazoles, pyradizines, pineridines; etc., anyoneof which may have-attached: thereto a longchain such as' dodecyl,

stea 'yl; etc. The substituted oxazolines, particu-. larly the. Z-hydroca-rbyl substituted oxazolines,

are veryefiective. The molecular weight of the saltg-as; a;whole maygoas-high as 1500, but the: molecular weight should preferably not g0 bove: 8.8

Illustrative; examples of suitable quaternaryammonium bases are: trimethyl benzyl ammo hydroxide, dimethyl benzyl cetyl ammoniumzhydroxide, stearyl triethyl ammonium hydrsx' tc.

I --not known just how the present class of inhibitors act to prevent corrosion of steel under the conditions employed in the present invention. Sufiice it to say that they have been found to actiefiectively; This is surprising in view of the turbulence of flow in the system and the low concentrations of inhibitor (less than about bonphase; so it would seem that they wouldv be dissolved and swept away bythe turbulent Suitable flow ofthis. phase, leaving: the surface. of; the. metal open to attack by: the. swiftly churning; aqueous carbonic acid present.

The present inhibitors function in the. specified:

system without the necessity of any added free.

bases such as ammonia, amines, organic: hydroxides, inorganic hydroxides... etc. Although free bases may bev addedto cr be present in the; sys-- tem, sofar'as is known, the inhibitors: of, the

present invention act independently of .free;

bases; When free. bases are added tn gas-com densate wells,. a deleterious efiect is; brought. about due to; the rise in the: pH value of the aqueous. phase to a point; that calcium ormag nesium. ions normally present exceed their solu bility product withinorganic salt-anions present. and precipitate; as salts. The latter causes ob.-: structionsor stopages'inthe wells. On the other: hand, the present inhibitors function. without. substantially changingthe pH of the: system, in gas-condensate wells. or the like;

The p esent agents may be, introduced. into distillate; (condensate) wells in various Ways. For example, tubin of; relatively small diameter may be run down the center of the production tube'of. such agwelliti); approximately the bottom.

end thereof, and a solution of. the present.

agent(s) may be, ump d. throu h the small diameter tubing so as to enter the well. streamnear the bottom of theiwell tube therising tur-= bulent; flow will; thencarry the injected. agent. p

throu h he. b h iollslyrthe corrosioninhibitQIS. may be, added. or: introduced into the wells by other means; or; methods, depending. in. part, on whether the. wells,.are, operated through. the, casings orthrough: tubing; disposed in; suchcasings. Also, itis clear thatthe inhibitors may be introducedintothe top of the well: andallowed to flow down, or may be forced to anygiven nOint.

the conditionsemployed, (e. g;, such solvents; as.

esters, alcohols, ketones, etc), may be used' forpreparing an inhibitQrysolution, although it is preferable to employ light gasolines or normally liquid'or liquefied condensates fromthewell that is to be treated: In the alternative, a suitable crude; oilorcrude'oil fraction (whether refined or not) is--also efficacious as ameans of forming; a .fiuid solution which canv be flowed or forced" into, thesecondensate wells;' In some cases it is advantageous to use a more or less. concentrated solution or dispersion (as up to, aboutpfill." wt. of, the agent(s)') in a suitable fluid medium such as. a diesel oil;v The amount of, solventin the inhibitor solution is so small, relativeto the. volume-of liquid in thesystem treated therewith, thatv it does. not materially affect the. normal operation. of the well,v

The agents of the present invention employed in the operation of light gasoline gas-condensate wells havernot caused emulsion troubles. However; in cases-where} undesirable emulsification isproduced for one reason or another, this can beprevented or inhibited by the addition of a wide variety of emulsion-breakers or demulsifiers, such as 2-ethyl hexanol, lauryl alcohol, octadecanol, high and low molecular weight silicones and organic silicates.

For purposes of further illustration, reference will now be made to the following examples, it being understood that there is no intention of being limited necessarily to the specific conditions disclosed therein. In these examples steel plates inch width, 5% inch length sandblasted coldrolled steel strips) were placed in oil-container pressure-bottles containing g. of a water solu-.

tion having 0.05 wt. per cent of sodium chloride and 50 g. of iso-octane containing in some cases a hydrocarbon-soluble additive of the present invention. In certain cases, the water phase also contained 0.05 wt. per cent of acetic acid. The concentration of the hydrocarbon soluble additive was based upon the iso-octane (hydrocarbon) content. The contents of each bottle were then saturated with carbon dioxide gas as follows: Air was displaced by passing a carbon dioxide to the bottom of each bottle for approximately minutes. aqueous phase was measured. Carbon dioxide was again passed in as previously, for about 5 minutes, and the operation repeated until the pH of the aqueous phase was constant. The prepared bottles were then tightly closed and the stoppers wired on to withstand the pressure developed at elevated temperatures. The bottles were then rotated end-over-end at 60 R. P. M. at a temperature of approximately 65 C. for a period ranging from 18 to 24 hours. At the end of this time the corrosion rates were measured for each steel plate. The results obtained from following the above-described technique are ven below.

Example I A series of steel plates were subjected to the above treatment in a container having 50 grams of iso-octane and 10 grams of water, the latter containing 0.05 wt. per cent of sodium chloride.'

No corrosion inhibitor was present. An analysis of the thus treated plates showed that the average corrosion rate was about 21.0 mils per year.

In another series, the steel plates were likewise treated except that the water phase, in addition to the sodium chloride also contained 0.05 wt. per cent of acetic acid (based on the water). In this case the average corrosion rate was found to be 39.0 mils per year.

Erample II Steel plates of the above type were treated in the same manner in the absence of acetic acid but in the presence of a reaction product formed by the interaction of equimolar amounts of 2 (heptadecen 8 yl) 4 methyl 4 (1 hydroxypropyl)-2-cxazoline and of monobasic oilsolubl'e petroleum sulfonate acids, this reaction product being employed in concentrations of 0.005 wt.% and 0.01 wt.%, as calculated on the iso-octane present in the mixture. The corrosion rates were found to be 0.9 and 0.5 mil per year, respectively.

When the above test was repeated with the same additive and in the presence of 0.05 wt.% of acetic acid, the corrosion rate was about 1.3 mils per year.

- Example III When the steel plates were treated as above described, in the absence of acetic acid, but in Then, the pH value of the the presence of an additive prepared from a mixture. of. oil-soluble substituted: oxazoline compounds, sold under the trade name of Alkatergc O and a corresponding mol equivalent of oilsoluble petroleum sulfonic acids employed to form the additive used in Example 11, which additive was used in concentrations of 0.005%, 0.01% and 0.03% (as calculated on the iso-octane content). the corrosion rates were 1.7, 0.5 and 1.2 mils per year, respectively.

Example IV When the steel plates were treated as described above, in the absence of acetic acid, but in the presence of an additive composition composed of a low viscosity index lubricating oil containing 2.5 wt.% of oil-soluble sodium mahogany petroleum sulfonates, 2.5 wt.% of oleic acid and 0.5 wt.% of sodium oleate, and when this.com-

.position was used in concentrations of 0.0011

0.0023% and 0.014% (as calculated on the sodium petroleum sulfonates content relative tothe liquid iso-octane present) the corrosion .rates were 1.8, 1.6 and 1.5 mils per year, respectively.

Example V When the steel plates were treated as above described in the presence of oil-soluble sodium mahogany petroleum sulfonates employed in concentrations of 0.005%, 0.01% and 0.06%, based on the iso-octane, the corrosion rates were 2.0, 1.5 and 0.7 mils per year, respectively.

Example VI Example VII When the steel plates were treated as described above, in the absence of acetic acid, but in the presence of an additive composed of 3.2 wt.% of oil-soluble sodium mahogany petroleum sulfonates dissolved in a blend of approximately 22 wt.% of a low viscosity index lubricating oil and about wt.% of a mineral spirits petroleum distillate (the remainder including about 22 wt.% of ammonium ricinoleate) about 0.8 wt.% of n-butanol, and about 1.1 wt.% of lard oil, it was found that by using this additive in concentrations (calculated on the ratio of petroleum sulfonates to the liquid iso-octane) of0.004%, 0.012% and 0.016%, the corrosion rates were 0.2, 0.3 and 0.3 mils per year, respectively; in similar runs in the presence of acetic acid, the corrosion rates were 3.0, 1.2 and 1.9 mils per year, respectively.

Example VIII hydrocarbon sulfonates relative to the liquid isoapeasoo :octane) were 0.0022% and 0.003153%, the corrosion rates were round to be 2.0'and 1.8 mils per year,

- respectively.

Example IX thick, inch diameter plates having a 1 inch diameter orifice in the center, said plate being -at a flanged joint upstream from the wellhead choke. After 89 days of injection it was found that the corrosion rate had been reduced to less than 1 mil per day.

Example X When the test of Example V is repeated using van equivalent amount of the barium salt of a sulfonated wax phenol, a similarly substantial reduction in corrosion is obtained.

Example XI When the procedure of Example IV is repeated, but using a sodium dialkylnaphthalene sulfonate, or the cyclohexylammonium salt of sulfonated sperm oil, instead of the calcium petroleum mahogany sulfonates, similar results are obtained.

The introduction of a number of the above described sulfonate salt additives into well streams of gas-condensate wells'in the above indicated concentrations and also in higher practicable amounts as described according to this invention in the above specification, have resulted in decrease in the iron content of the effluent water and in a significantly decreased corrosion rate of steel coupons placed within the well stream. The process of the present invention is also .applicable to treatment of wells in which the hydrocarbon phase, under the operating conditions, -is substantially solely in the gaseous state.

This application .is a continuation-in-part of application Serial No. 764,593. filed July 29, 1947, now abandoned.

We claim as our invention:

1. The method of treating a hydrocarbon-containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonicacid of Well metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount otaqueous carbonic acid, which 'system in a state of agitated'fiow at a temperature of between about C. and about 125 C.

and under a pressure of between about fifteen .0

and seven thousand pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mix- .ing with said-systeman amount of below approximately one weight per cent and above ap proximately 0.0001 weight per cent of the liquid hydrocarbon phase contacted, of an oil-soluble sodium petroleum mahogany sulfonate salt having a molecular weight between about 450 and about 650, said salt having an .oleophilic residue containing at least about 16 carbon atoms.

2. The method of treating a hydrocarbon containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas phase, a liqueminor. amount of aqueous carbonic acid, which system in a. state of agitated flow at. temperature of between. about 45' C- and about C. and under a pressure of between about fifteen and about seven thousand pounds per square inch absolute, comes. in contact with corrodible well parts, which method includes. the step of mixing with said system an amount of below approximately 1 weight 'per cent and above approximately 0.0001 weightper cent of the liquid hydrocarbon phase contacted, of an oil-soluble alkali metal petroleum mahogany sulfonate salt having a molecular weight between about 450 and about 650, said salt having an oleophilic residue containing at least about 16 carbon atoms.

3. The method of treating a hydrocarbon containing System in its natural state in a well .for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas phase, a lique-.

vfled normally gaseous hydrocarbon phase and a minoramount of aqueous carbonicacid, which system in a state of agitated flow ata temperature of between about 45 C. and about 125 C. and under a, pressure of between about fifteen and about seven thousand pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mixing with said system an amount of below approximately one weight per cent and above approximately 0.0001 weight per cent of the liquid hydrocarbon phase contacted, of an oil-soluble alkali metal petroleum mahogany sulfonate salt having a molecular weight between about 400 and about 880, said salt having an oleophilic residue containing at least about 16 carbon atoms.

4. The method of treating a hydrocarbon containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic acid, which system in a state of agitated flow at a temperature of between about 45 C. and about 125 C; and under a pressure of between about fifteen and about seven thousand pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mixing with said system an amount of below approximately one weight per cent and above approximately 0.0001 weight per cent of the liquid hydrocarbon phase contacted, of an oil-soluble alkaline earth metal petroleum mahogany sulfonate salt having a molecular weight between about 400 and about 300, said salt having an oleophilic residue containing at least about 16 carbon atoms.

5. The method of treating a hydrocarbon containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of well "metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic acid, which system in a state of agitated flow at a temperature of between about 45 C. and about 125 C. and under a pressure of between about fifteen and about seven thousand pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mixing with said system an amount of below approximately one weight per cent and above approximately 0.0001 weight per cent of the liquid hydrocarbon phase contacted, of an oil-soluble base metal petroleum mahogany sulfonate salt having a molecular weight between about 400 and about 880, said salt having an oleophilic'residue containing at least about 16 carbon atoms.

6. The method of treating a hydrocarbon containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic acid, which system in a state of agitated flow at a temperature of between about 45 C. and about 125 C. and under a pressure of between about fifteen and about seven thousand pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mixing with said system an amount of below approximately one weight per cent and above approximately 0.0001 weight per cent of an oil-soluble sodium salt of an aryl sulfonic acid having a molecular weight between about 450 and about 650, said salt having an oleophilic residue containing at least about 16 carbon atoms.

7. The method of treating a hydrocarbon containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of Well metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic acid, which system in a state of agitated flow at a temperature of between about 45 C.and about 125 C. and under a pressure of between about fifteen and about seven thousand pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mixing with said system an amount of below approximately one weight per cent and above approximately 0.0001 weight per cent of an oil-soluble sodium salt of an organic sulfonic acid having a molecular weight between about 400 and about 880, said salt having an oleophilic residue containing at least about 16 carbon atoms.

8. The method of treating a hydrocarbon containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas, phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic acid, which system in a state of agitated flow at a temperature of between about 45 C. and about 125 C. and under a pressure of between about, fifteen and about seven thousand pounds per square inch absolute,

comes in contact with corrodible well parts, which method includes the step of mixing with said system an amount of below approximately one weight per cent and above approximately 0.0001 weight per cent of an oil-soluble salt of an organic sulfonic acid having a molecular weight between about 450 and 880, said salt having an oleophilic residue containing at least about 16 carbon atoms.

9. The method of treating a hydrocarbon containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase and a minor 12 amount of aqueous carbonic acid, which system in a state'of agitated flow at a temperature of between about 45 C. and about Cland under a pressure of between about fifteen and about seven thousand pounds per square inch absolute, comes in contact with corrodible well parts, which method'includes the step of mixing with said system an amount of below approximately one weight per cent and above approximately 0.0001/ weight per cent of an oil-soluble oxazoline salt of an aryl sulfonic acid having a molecular weight between about 450 and about 650, said salt having an oleophilic residue containing at least about 16 carbon atoms.

10. The method of treating a hydrocarbon-containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxidizing gas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic acid, which system in 'a state of agitated flow under a pressure of between about fifteen and seven thousand pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mixing with said system an amount of below approximately one weight per cent and above approximately 0.0001 weight per cent'of the liquid hydrocarbon phase contacted, of an oilsoluble sodium petroleum mahogany sulfonate salt having a molecular weight between about 450 and about 650, said salt having an oleophilic residue containing at least about 16 carbon atoms. 11. The method of treati'ng a hydrocarbon containing system in its natural state in a well for the purpose of inhibiting corrosion by aqueous carbonic acid of well metal parts, said system comprising a non-oxiding gas phase, a liquefied normally gaseous hydrocarbon phase and a minor amount of aqueous carbonic acid, which system in a state of agitated flow under a pressure of between about fifteen and about seven thousand pounds per square inch absolute, comes in contact with corrodible well parts, which method includes the step of mixing with said system an amount of below approximately one weight per cent and above approximately 0.0001 weight per cent of an oil-soluble salt of an organic sulfonic acid having a molecular weight between about 450 and about 880; said salt having an oleophilic residue containing at least about 16 carbon atoms.

AARON WACHTER. WILIF'RID W. NEWSCHWANDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Blair et al Apr. 5, 1949 

8. THE METHOD OF TREATING A HYDROCARBON CONTAINING SYSTEM IN ITS NATURAL STATE IN A WELL FOR THE PURPOSE OF INHIBITING CORROSION BY AQUEOUS CARBONIC ACID OF WELL METAL PARTS, SAID SYSTEM COMPRISING A NON-OXIDIZING GAS PHASE, A LIQUEFIED NORMALLY GASEOUS HYDROCARBON PHASE AND A MINOR AMOUNT OF AQUEOUS CARBONIC ACID, WHICH SYSTEM IN A STATE OF AGITATED FLOW AT A TEMPERATURE OF BETWEEN ABOUT 45* C. AND ABOUT 125* C, AND UNDER A PRESSURE OF BETWEEN ABOUT FIFTEEN AND ABOUT SEVEN THOUSAND POUNDS PER SQUARE INCH ABSOLUTE COMES IN CONTACT WITH CORRODIBLE WELL PARTS, WHICH METHOD INCLUDES THE STEP OF MIXING WITH SAID SYSTEM AN AMOUNT OF BELOW APPROXIMATELY ONE WEIGHT PER CENT AND ABOVE APPROXIMATELY 0.0001 WEIGHT PER CENT OF AN OIL-SOLUBLE SALT OF AN ORGANIC SULFONIC ACID HAVING A MOLECULAR WEIGHT BETWEEN ABOUT 450 AND
 880. SAID SALT HAVING AN OLEPHILIC RESIDUE CONTAINING AT LEAST ABOUT 16 CARBON ATOMS. 